180 sonographically guided percutaneous biopsies in a variety of anatomic regions (abdomen, 110; thorax, 33; neck, 28; breast, 4; extremity, 5) were retrospectively reviewed to evaluate the percentage of correct histologic diagnoses of malignant tumours. A positive diagnosis of malignancy was established in 101 (96 %) of 107 malignant tumours. A correct histologic classification was achieved in 79 (73 %) of 108 malignant tumours by means of cytologic and histologic examination of the tissue acquired. Correct histologic classification of malignant tumours depends on several factors including a) needle diameter, b) location of the tumour, c) clinical constellation and, most important d) the complexion of the tumour histology. The percentage of correct histological diagnoses varied between carcinomas (79 %), Hodgkin lymphomas (100 %), non-Hodgkin lymphomas (45 %), sarcomas (50 %) and carcinoid tumours (0 %). Histological classification of malignant tumours by means of percutaneous biopsy can be improved by multiple biopsies of different portions of the tumour and by using larger cutting needles.